f{-}wanted\{\$z,\$wanted\}(${\it es}$;$e_{1}$;$j$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$es{-}first{-}from(${\it es}$;$e_{1}$;$<$es{-}loc(${\it es}$; $e_{1}$), $j$, "\$z"$>$;"\$wanted")